390 



METAZOAN PHYLA 



independently and it is stated that the pecuUar structure of the lids 

 makes it possible for the animal to locate objects very exactly. The 



Scufe 



Ear opening 



Fig. 276. — Heads of a bull snake, Pituophis sayi (Schlegel), and of a lizard, Plestiodon 

 septentrionalis Baird. A, head of the snake, from the side. B, from below. C, head of the 

 lizard, from the side. D, from below. A and B, X % ; C and D, X 2. 



tongue, which is club-shaped and abundantly provided with a sticky 

 secretion, can be protruded to a distance of six inches or more. This 



enables the chemeleon to use its 

 tongue for capturing insects, which 

 constitute its entire diet. Cha- 

 meleons are generally oviparous, 

 although a few produce living young. 

 They are famed for their power of 

 changing color, which is due to the 

 presence of chromatophores in the 

 skin, affected both by outside stimuli 

 and by stimulation by the nervous 

 system. 



417. Lizards. — The lizards are 

 the most typical of the reptiles. 

 The limbs are well-developed and 

 modified for running, climbing, or 

 digging. Rarely limbs are absent, 

 in which case the animal has very 

 much the appearance of a snake. 

 This is true of the so-called glass 

 snakes of Europe and America, which 

 are really lizards, and of some bur- 

 rowing lizards, known as worm lizards, found in southern United States. 

 Legless lizards may be distinguished from snakes (Fig. 276) by the 



Fig. 277. — Wall gecko, Tarentola 

 mauritanicus (Linnaeus), of southern 

 Europe. {From Brehm, " Thierleben.") 



xVs. 



